Devices communicating over network links are becoming increasingly popular especially when the network links are wireless links typically formed from radio frequency links. One basic mode in which most radio-frequency-based wireless devices are designed to operate in is an infrastructure (“IS”) mode. In the infrastructure mode, which is also sometimes referred to as the managed network mode, each wireless device communicates with another device in the network through an access point of the network. The access point functions as a bridge, repeater, gateway, and firewall between wireless devices for a given coverage area and wired devices of the network.
Wireless networks are also used for the transfer of multimedia data streams, such as video-on-demand, video-conferencing, and on-line brokerage services. Such data streams are time-sensitive, as any significant delay in the transfer of data packets of such data streams degrades the quality of the service provided to the data stream.
The bandwidth over a wireless communication channel is limited, and relatively narrow. To best utilise the limited bandwidth, while meeting the delay requirements of data to be transmitted by multiple wireless devices over the shared communication channel, the concept of Quality of Service (QoS) has been introduced. The access point, and in particular a packet scheduler in the access point, attempts to apportion bandwidth of the communication channel to the wireless devices to satisfy the QoS requirements of the data to be transferred. For example, in a network that supports multimedia services, the packet scheduler typically gives a higher priority to time-sensitive multimedia data streams so that their packets are transmitted with less delay than packets of data streams less affected or unaffected by delay.
Data packets from the various wireless device sources are scheduled for transmission by the packet scheduler for a given duration, that duration being called a scheduling window. In general, the scheduling window is a submultiple of a Contention Free Period (CFP). During the CFP, the packet scheduler manages all access of the shared communication channel by polling the wireless devices in a slotted fashion.
However, the unreliability of the wireless communication channel makes packet scheduling for the shared wireless communication channel a challenging problem. Furthermore, in the case of data flows from wireless devices to the access point, known as uplink flows, the packet scheduler does not have instant knowledge of the flow state, which typically includes the size of the data queue at the wireless device, the size of the individual data frames to be transmitted over the wireless communication channel, the instantaneous physical transmission rate to be used by the wireless device, the QoS requirements of the flow (expressed in terms of delay, bandwidth, jitter, or any other relevant metric).
The QoS requirements differ from other flow state elements in that they are signalled during connection set up and therefore known in advance. The remainder of the flow state elements are dynamic. If the QoS requirements change during the lifetime of a connection, the new requirements are signalled to the access point.
The access point therefore relies on feedback information from the originating wireless devices. The feedback information is then interpolated, and packet scheduling is performed based on the interpolations.
With a large scheduling window, the interpolations may become inaccurate due to the unreliability of the wireless communication channel and inaccuracies in the interpolations. However, by reducing the duration of the scheduling window arbitrarily, an extra computational burden is placed on the access point.
Thus, a need clearly exists for selecting the duration of the scheduling window that is appropriate for the QoS requirements of the data flows, without incurring an extra computational burden.